Mucosal regeneration following injury involves restoration of normal regional patterns of functional and morphological gut differentiation and is a characteristic pathological feature of many gastrointestinal diseases including inflammatory bowel disease. The fibroblast growth factors (FGFs) are an important group of peptide growth factors that regulate morphogenic events during normal fetal development, and also regulate cellular function during wound-healing. The central hypothesis of this proposal is that members of the FGF family play a central role in the regulation of cellular events involved in epithelial injury- repair. The long term goals of this project will be to use in vitro, in vivo, and transgenic model systems to define the roles of FGFs in regulating epithelial differentiation, cell-renewal, cell-migration, and mucosal regeneration following epithelial injury such as is seen in IBD. The specific aims of the proposal are: specific aim 1) To determine the role of FGF-2 in regulating apoptosis and crypt stem cell survival in the intestinal epithelium following injury; specific aim 2) to determine the role of FGF receptor-mediated signal events in regulating apoptosis and crypt stem cell survival following radiation-injury; specific aim 3) To determine the role of FGFs in regulating intestinal epithelial apoptosis that is induced by T-cell activation in the gut. Initial studies have shown that expression of FGF-2, expression of cyclooxygenase-1, and prostaglandin synthesis are induced following radiation injury with a similar time course. We will determine whether FGF-2 regulates apoptosis, and/or crypt stem cell survival following gamma-irradiation through prostaglandin dependent or independent pathways by examining the effects of FGF-2 on apoptosis, cell survival, cell cycle arrest, expression of Bcl-2 related proteins, expression of Cox-1 and Cox-2, and prostaglandin synthesis in intestinal epithelial cells in culture and in FGF-2 -/-, Cox-1 -/- and Cox-2 -/- mouse lines. The role of specific FGF receptor-mediated signaling events in regulating radiation induced apoptosis and intestinal epithelial cell survival will be investigated in I407 cells and in transgenic mice expressing specific dominant-negative FGF receptors targeted to the intestinal epithelium and in mice lacking functional FGF receptor-3. To determine whether the effects of FGF-2 on radiation-induced apoptosis are similar to the effects of FGF-2 on apoptosis mediated by T-cell activation we will examine expression of FGF-2, Cox-1, Cox-2, Bcl related genes, prostaglandin synthesis and apoptosis in wild-type mice and FGF2 -/- mice treated at various times following systemic treatment with anti-CD3 or in DO11.10 transgenic mice after administration of OVA peptide.